Typically, an electric power system includes a plurality of power generation assets, which are spread over a geographic area. The electric power system also includes systems that consume power (loads) that may also be spread over the geographic area. The electric power system generally includes a grid, a network of electric power lines and associated equipment used to transmit and distribute electricity over the geographic area. The infrastructure of the grid, may include, but is not limited to devices for interconnection, control, maintenance, and improvement of the electric power system operation. Typically, the electric power system includes a centralized control system operatively connected to the power generation assets for controlling a power output of each of the power generation assets, for example, using processing logic. The network operator usually operates the centralized control system. The power output of the power generation assets controlled by the centralized control system may include, but is not limited to, an amount of electrical power, and/or a voltage for the electrical power.
The power generation assets include individual power generating stations. For example, the power generating stations may each serve a geographic region within the grid by delivering electrical power to such regions. The power generation assets may include any type of power source that generates electrical power at least partially from coal, water, a combustible fluid such as gasoline, natural gas, diesel fuel, etc., nuclear, wind, and/or solar energy.
For economic reasons and as one of the approaches to reduce the environmental impacts of fossil fuel power generation, renewable energy plants, such as wind farms having a larger power output, are being produced and wind farms with greater numbers of wind turbine generators are being brought into operation. The power output from the wind farms in the future may comprise a significantly larger part of the total power being supplied and transmitted along the transmission grid. At the same time, there is increasing concern about the transmission capacity available for new large-scale wind farms, and the stability issues limiting transmission capacity.
Wind energy is often used to generate electrical power at power plants via a plurality of wind turbines often referred to as wind farms, using, for example, the rotation of the wind turbines to drive electrical generators. Wind farms and their associated farm controllers can control reactive power supply, and to a more limited extent active power. For example, U.S. Pat. No. 7,119,452, U.S. Pat. No. 7,166,928, and U.S. Pat. No. 7,224,081 each describes voltage control for wind generators including a farm-level controller with a reactive power command and a wind turbine generator control system. Wind turbine generator voltage control may be provided by regulating the voltage according to a reference set by a higher-than-generator-level (substation or farm level) controller. Reactive power may be regulated over a longer term (e.g. few seconds) while wind turbine generator terminal voltage is regulated over a shorter term (e.g. fraction of a second) to mitigate the effect of fast grid transients.
As the density of wind farms in a given area increases, either from a single developer, or multiple developers, the likelihood of regulator interaction will increase. Additionally, the regulations from the grid operators are evolving to require improved voltage regulation from such wind plants. As such, there is a growing need for adjacent wind plants to cooperate in their VAR production and absorption in order to maintain a suitable level of tolerance in the voltage control.
Accordingly, a system and method for coordinating control of multiple renewable energy plants, such as wind farms, on a common point of regulation on a power grid by balancing the reactive power production of each participating plant so as to ensure that the plant operations meet the regulatory requirements imposed upon them would be welcomed in the art.